Images, whether still images or moving images (e.g., movies or video), are often represented as arrangements of picture elements called “pixels.” For example, a photograph printed on photographic paper may be scanned and represented in electronic form as an image composed of 307,200 pixels, arranged in a rectangle 640 pixels in width and 480 pixels in height. As another example, an “8 megapixel” digital camera may capture a rectangular image composed of over 8 million pixels. As a further example, a video camcorder may capture a video clip as a sequence of images, all 720×480 pixels in size. As a further example, a computer that is executing animation software may generate a movie clip composed of multiple 1920×1080 pixel images.
An image may be processed to generate another image. Specifically, an image modification algorithm, for example, a “filter algorithm” or simply a “filter,” may be used to generate an output image by modifying an input image. The input image is composed of input pixels, and the output image is composed of output pixels. The output image need not have the same size, shape, or dimensions as the input image, or even the same visual appearance for that matter. For example, filters may be used to brighten the input image, darken the input image, or alter the color of the input image to be more reddish or greenish in appearance.